Time-resolved photoelectron spectroscopy

In addition to the natural improvements expected in the accuracy of the measurements, and the increased scope in the types of systems examined, new techniques go beyond the issue of thermochemistry to allow for very detailed studies of reaction dynamics. The investigation by Zewail and co-workers of the reactivity of planar COT" on the femtosecond time scale is likely only the beginning. Time-resolved photoelectron spectroscopy, for example, has recently been used to map the potential energy surfaces for the dissociation of simple ions IBr and l2. " Although applications in the field of organic reactive molecules are likely far off, they are now possible. 

Hudock et al. [126] used the ab initio molecular dynamics multiple spawning method to go beyond the static picture based on PES and include the time dependent dynamical behavior and predict time-resolved photoelectron spectroscopy results. According to these results the first ultrafast component of the photoelectron spectra of uracil corresponds to relaxation on the S2 minimum rather than nonadiabatic transitions to the Si state. The authors suggest that the radiationless relaxation from... 

Ullrich S, Schultz T, Zgierski MZ, Stolow A (2004) Direct observation of electronic relaxation dynamics in adenine via time-resolved photoelectron spectroscopy. J Am Chem Soc 126 2262... 

Hudock HR, Levine BG, Thompson AL, Satzger H, Townsend D, Gador N, Ullrich S, Stolow A, Martinez TJ (2007) Ab initio molecular dynamics and time-resolved photoelectron spectroscopy of electronically excited uracil and thymine. J Phys Chem A 111 8500-8508... 

D. M. Neumark We are currently carrying out somewhat different femtosecond experiments in which time-resolved photoelectron spectroscopy is used to probe the photodissociation dynamics of negative ions. In these experiments, an anion is photodissociated with a femtosecond laser pulse. After a time delay, the dissociating anion is pho-todetached with a second femtosecond pulse and the resulting photoelectron spectrum is measured. The photoelectron spectrum as a function of delay time provides a detailed probe of the anion photodissociation dynamics. First results have recently been obtained for the photodissociation of I2. 

TIME-RESOLVED PHOTOELECTRON SPECTROSCOPY OF NONADIABATIC DYNAMICS IN POLYATOMIC MOLECULES... 

We turn now to a more detailed description of the photoionization probe step in order to clarify the ideas presented above. Time-resolved photoelectron spectroscopy probes the excited-state dynamics using a time-delayed probe laser pulse that brings about ionization of the excited-state wave packet, usually with a single photon... 

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